A high performance defoamer, RXJ, is synthesized with aviation kerosene as the base fluid, aluminum di-stearate, oleic acid, iso-octanol, and tri-butyl phosphate. The optimum conditions for the synthesis are as follows: add 6% of aluminum di-stearate in aviation kerosene and allow for dissolution at 70 V. for 10-20 min, then add the rest reagents. The key to the synthesis is the thermal dissolution of aluminum di-stearate in aviation kerosene. At concentration of 0.2% of RXJ, base fresh water mud has a density recovery of not less than 92%, and base saltwater (4% salt) mud not less than 95%. Field application in Well Majing-26 showed that, adding 0.1%-0.2% of RXJ, foam in the drilling fluid disappeared swiftly, and the defoaming effect lasted for 4-5 days.